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GCSE Edexcel Separate Physics > SP5 Light and the Electromagnetic Spectrum > Flashcards

SP5 Light and the Electromagnetic Spectrum Flashcards

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1
Q

What is a normal?

A

A line drawn at right angles to the barrier or mirror in a ray diagram

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2
Q

What is a ray diagram?

A

A way of modelling what happens when light is reflected or refracted

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3
Q

Where are the angle of incidence and the angle of refraction measured from?

A

The normal

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4
Q

State the law of reflection

A

When waves are reflected, the angle of reflection is equal to the angle of incidence

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5
Q

What happens to light when it travels through different materials?

A

It changes speed and direction

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6
Q

Define refraction

A

The change in the direction of a wave at a boundary

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7
Q

When is there no change in direction when a light ray hits the boundary?

A

If it hits the boundary at right angles

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8
Q

What is the medium light travels the fastest in?

A

Air

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9
Q

What is the medium light travels the slowest in?

A

Solids (glass)

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10
Q

What happens when light enters into a medium wherein it travels slower than the previous one?

A

It bends towards the normal

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11
Q

What happens when light enters into a medium wherein it travels faster than the previous one?

A

It bends away from the normal

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12
Q

What is total internal reflection?

A

Sometimes, when light is moving into a less dense material as compared to one it was already in, instead of being refracted, it is reflected inwards

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13
Q

When does total internal reflection occur?

A

The angle of incidence is greater than the critical angle and the incident material is denser than the second material

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14
Q

What are the two conditions for total internal reflection?

A
  • angle of incidence > critical angle
  • the incident material is denser than the second material
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15
Q

What is the critical angle?

A

The angle of incidence wherein the angle of refraction is 90 degrees

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16
Q

Why can luminous objects be seen?

A

They give off light

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17
Q

What is specular reflection?

A

Reflection from a smooth, flat surface

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18
Q

What is total internal reflection used in?

A
  • prisms
  • optical fibres
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19
Q

Describe a typical image produced from a specular reflection

A
  • upright
  • virtual
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20
Q

Define diffuse reflection

A

Instead of forming an image, the reflected light is scattered in all directions

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21
Q

What kind of image does a diffuse reflection cause?

A
  • distorted
  • no image at all
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22
Q

State the colours in order of increasing frequency and decreasing wavelength

A
  • red
  • orange
  • yellow
  • green
  • blue
  • indigo
  • violet
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23
Q

When is light absorbed?

A

When white light shines on an opaque object

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24
Q

Give an example of the transmission of a wave at a boundary

A

Transparent objects, such as glass transmit waves because they barely absorb any light

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25
Q

What are filters?

A

Pieces of transparent materials that absorb some of the colours in white light and transmit a specific colour

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26
Q

When does an object appear black?

A

When it absorbs all wavelengths of visible light

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27
Q

What is a lens?

A

A shaped piece of transparent glass or plastic that refracts light

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28
Q

What does the power of a lens describe?

A

How much it bends light that passes through it

29
Q

Describe a convex lens

A
  • thicker in the middle than it is at the edges
  • shaped like an almond/ eye
30
Q

What is the focal point of a lens?

A

The point where all horizontal rays meet after passing through the lens

31
Q

What is the focal length?

A

The distance between the lens and the focal point

32
Q

What does a convex lens do?

A

Focuses light inwards

33
Q

What is a convex lens used in?

A
  • magnifying glasses
  • to correct long-sightedness
  • binoculars
34
Q

Describe a concave lens

A
  • ‘caves’ inwards
  • thinner at the centre as compared to the edge
35
Q

What does a concave lens do?

A

Spreads light outwards

36
Q

What is a concave lens used for?

A

To correct short-sitedness

37
Q

How is a concave lens drawn on a ray diagram?

A

With a straight line with arrows facing inwards

38
Q

How is a convex lens drawn on a ray diagram?

A

A straight line with arrows on both sides

39
Q

What is a real image?

A

An image produced on the opposite side of the lens to the object

40
Q

What is a virtual image?

A

Appear to come from the same side of lens to object

41
Q

What type of waves are electromagnetic waves?

A

Transverse waves

42
Q

What are common properties amongst all electromagnetic waves?

A
  • transfer energy as radiation from the source of waves to an absorber
  • can travel through a vacuum
  • travel everywhere at the same speed: 3x 10^8 m/s
43
Q

What are EM waves with a slightly higher frequency than visible light called?

A

Ultraviolet

44
Q

What are EM waves with a slightly lower frequency than visible light called?

A

Infrared

44
Q

What is IR used for?

A
  • electrical heating
  • cooking food
  • optical fibres
  • security cameras
  • thermal imaging cameras
44
Q

What are the seven groups within the EM spectrum?

A
  • radio waves
  • microwaves
  • IR
  • visible light
  • UV
  • X rays
  • Gamma rays
44
Q

What are radio waves used for?

A

Communication: eg: broadcasting TV and radio communications and satellite transmissions. They can also induce oscillations in electrical circuits, as well as being produced by oscillations in electrical circuits

45
Q

What waves can be refracted by the atmosphere?

A

Radio waves

45
Q

What are the uses of microwaves?

A
  • cooking food
  • communications
  • satellite comms
45
Q

What waves are harmful to the human body?

A

Infrared, microwaves, ultraviolet, radio waves, x rays and gamma rays

46
Q

How can a system stay at a constant temperature?

A

It must absorb the same amount of power as it radiates

47
Q

What is power?

A

The amount of energy transferred in a certain time

48
Q

What is Earth’s temperature dependant on?

A
  • concentration of greenhouse gases
  • rates of which light and IR radiation are:
    —> absorbed by the Earth’s surface and atmosphere
    —> emitted by the Earth’s surface and atmosphere
49
Q

What happens when light and IR radiation are absorbed by the Earth’s surface?

A
  • planet’s internal energy increases
  • surface gets hotter
  • some energy transferred to the atmosphere by conduction and convection
50
Q

What happens when the Earth radiates lower frequency IR radiation?

A
  • some absorbed by greenhouse gases
  • greenhouse gases emit IR radiation in all directions; some out into space and some back towards earth
51
Q

What is the ‘greenhouse effect’?

A

When the greenhouse gases in the Earth’s atmosphere trap heat, warming the Earth’s surface

52
Q

What do greenhouse gases do?

A

Stabilise the surface temperature of the Earth, allowing the planet to sustain life

53
Q

How is temperature affected if a system absorbs more power than it radiates?

A

It increases

53
Q

What is causing an enhanced greenhouse effect?

A

Human activities such as deforestation and burning fossil fuels release more carbon dioxide into the atmosphere, which ends up retaining more heat

53
Q

What is the relationship between wavelength and frequency of all EM waves?

A

Inversely proportional
- as wavelength increases, frequency decreases
- as frequency increases, wavelength decreases

54
Q

How is temperature affected if a system radiates more power than it absorbs?

A

It decreases

55
Q

How is the temperature of the Earth maintained?

A

By the amount of energy received and emmitted by the sun

56
Q

What are the uses of UV?

A
  • disinfectants
  • security marking
  • fluorescent lamps
  • detecting forged bank notes
57
Q

What are the uses of Gamma rays?

A
  • sterilise foods and surgical instruments
  • detection of cancer
  • radiotherapy
58
Q

What are the uses of xrays?

A
  • observing the internal structure of objects
  • airport security scanners
  • medical x rays
59
Q

What are the dangers of microwaves?

A

Internal heating of body cells

60
Q

What is the danger of IR?

A

Skin burns

61
Q

What is the danger of UV?

A

Damage to surface cells and eyes, which leads to skin cancer

62
Q

What are the dangers of X rays and gamma rays?

A

Mutations or damage to body cells

GCSE Edexcel Separate Physics (18 decks)

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